ipv6: lockless IPV6_RECVERR implemetation

np->recverr is moved to inet->inet_flags to fix data-races.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/ipv6.h

@@ -243,8 +243,7 @@ struct ipv6_pinfo {
 	} rxopt;
 
 	/* sockopt flags */
-	__u16			recverr:1,
-	                        sndflow:1,
+	__u16			sndflow:1,
 				repflow:1,
 				pmtudisc:3,
 				padding:1,	/* 1 bit hole */

include/net/inet_sock.h

@@ -274,6 +274,7 @@ enum {
 	INET_FLAGS_AUTOFLOWLABEL_SET = 23,
 	INET_FLAGS_AUTOFLOWLABEL = 24,
 	INET_FLAGS_DONTFRAG	= 25,
+	INET_FLAGS_RECVERR6	= 26,
 };
 
 /* cmsg flags for inet */

include/net/ipv6.h

@@ -1303,9 +1303,7 @@ static inline int ip6_sock_set_v6only(struct sock *sk)
 
 static inline void ip6_sock_set_recverr(struct sock *sk)
 {
-	lock_sock(sk);
-	inet6_sk(sk)->recverr = true;
-	release_sock(sk);
+	inet6_set_bit(RECVERR6, sk);
 }
 
 static inline int __ip6_sock_set_addr_preferences(struct sock *sk, int val)

net/dccp/ipv6.c

@@ -185,7 +185,7 @@ static int dccp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 		goto out;
 	}
 
-	if (!sock_owned_by_user(sk) && np->recverr) {
+	if (!sock_owned_by_user(sk) && inet6_test_bit(RECVERR6, sk)) {
 		sk->sk_err = err;
 		sk_error_report(sk);
 	} else {

net/ipv4/ping.c

@@ -581,7 +581,7 @@ void ping_err(struct sk_buff *skb, int offset, u32 info)
 	 *	4.1.3.3.
 	 */
 	if ((family == AF_INET && !inet_test_bit(RECVERR, sk)) ||
-	    (family == AF_INET6 && !inet6_sk(sk)->recverr)) {
+	    (family == AF_INET6 && !inet6_test_bit(RECVERR6, sk))) {
 		if (!harderr || sk->sk_state != TCP_ESTABLISHED)
 			goto out;
 	} else {

net/ipv6/datagram.c

@@ -305,11 +305,10 @@ static void ipv6_icmp_error_rfc4884(const struct sk_buff *skb,
 void ipv6_icmp_error(struct sock *sk, struct sk_buff *skb, int err,
 		     __be16 port, u32 info, u8 *payload)
 {
-	struct ipv6_pinfo *np  = inet6_sk(sk);
 	struct icmp6hdr *icmph = icmp6_hdr(skb);
 	struct sock_exterr_skb *serr;
 
-	if (!np->recverr)
+	if (!inet6_test_bit(RECVERR6, sk))
 		return;
 
 	skb = skb_clone(skb, GFP_ATOMIC);
@@ -344,12 +343,11 @@ EXPORT_SYMBOL_GPL(ipv6_icmp_error);
 
 void ipv6_local_error(struct sock *sk, int err, struct flowi6 *fl6, u32 info)
 {
-	const struct ipv6_pinfo *np = inet6_sk(sk);
 	struct sock_exterr_skb *serr;
 	struct ipv6hdr *iph;
 	struct sk_buff *skb;
 
-	if (!np->recverr)
+	if (!inet6_test_bit(RECVERR6, sk))
 		return;
 
 	skb = alloc_skb(sizeof(struct ipv6hdr), GFP_ATOMIC);

net/ipv6/ipv6_sockglue.c

@@ -481,6 +481,13 @@ int do_ipv6_setsockopt(struct sock *sk, int level, int optname,
 	case IPV6_DONTFRAG:
 		inet6_assign_bit(DONTFRAG, sk, valbool);
 		return 0;
+	case IPV6_RECVERR:
+		if (optlen < sizeof(int))
+			return -EINVAL;
+		inet6_assign_bit(RECVERR6, sk, valbool);
+		if (!val)
+			skb_errqueue_purge(&sk->sk_error_queue);
+		return 0;
 	}
 	if (needs_rtnl)
 		rtnl_lock();
@@ -943,14 +950,6 @@ int do_ipv6_setsockopt(struct sock *sk, int level, int optname,
 		np->pmtudisc = val;
 		retv = 0;
 		break;
-	case IPV6_RECVERR:
-		if (optlen < sizeof(int))
-			goto e_inval;
-		np->recverr = valbool;
-		if (!val)
-			skb_errqueue_purge(&sk->sk_error_queue);
-		retv = 0;
-		break;
 	case IPV6_FLOWINFO_SEND:
 		if (optlen < sizeof(int))
 			goto e_inval;
@@ -1380,7 +1379,7 @@ int do_ipv6_getsockopt(struct sock *sk, int level, int optname,
 		break;
 
 	case IPV6_RECVERR:
-		val = np->recverr;
+		val = inet6_test_bit(RECVERR6, sk);
 		break;
 
 	case IPV6_FLOWINFO_SEND:

net/ipv6/raw.c

@@ -291,6 +291,7 @@ static void rawv6_err(struct sock *sk, struct sk_buff *skb,
 	       struct inet6_skb_parm *opt,
 	       u8 type, u8 code, int offset, __be32 info)
 {
+	bool recverr = inet6_test_bit(RECVERR6, sk);
 	struct ipv6_pinfo *np = inet6_sk(sk);
 	int err;
 	int harderr;
@@ -300,7 +301,7 @@ static void rawv6_err(struct sock *sk, struct sk_buff *skb,
 	   2. Socket is connected (otherwise the error indication
 	      is useless without recverr and error is hard.
 	 */
-	if (!np->recverr && sk->sk_state != TCP_ESTABLISHED)
+	if (!recverr && sk->sk_state != TCP_ESTABLISHED)
 		return;
 
 	harderr = icmpv6_err_convert(type, code, &err);
@@ -312,14 +313,14 @@ static void rawv6_err(struct sock *sk, struct sk_buff *skb,
 		ip6_sk_redirect(skb, sk);
 		return;
 	}
-	if (np->recverr) {
+	if (recverr) {
 		u8 *payload = skb->data;
 		if (!inet_test_bit(HDRINCL, sk))
 			payload += offset;
 		ipv6_icmp_error(sk, skb, err, 0, ntohl(info), payload);
 	}
 
-	if (np->recverr || harderr) {
+	if (recverr || harderr) {
 		sk->sk_err = err;
 		sk_error_report(sk);
 	}
@@ -587,7 +588,6 @@ static int rawv6_send_hdrinc(struct sock *sk, struct msghdr *msg, int length,
 			struct flowi6 *fl6, struct dst_entry **dstp,
 			unsigned int flags, const struct sockcm_cookie *sockc)
 {
-	struct ipv6_pinfo *np = inet6_sk(sk);
 	struct net *net = sock_net(sk);
 	struct ipv6hdr *iph;
 	struct sk_buff *skb;
@@ -668,7 +668,7 @@ static int rawv6_send_hdrinc(struct sock *sk, struct msghdr *msg, int length,
 error:
 	IP6_INC_STATS(net, rt->rt6i_idev, IPSTATS_MIB_OUTDISCARDS);
 error_check:
-	if (err == -ENOBUFS && !np->recverr)
+	if (err == -ENOBUFS && !inet6_test_bit(RECVERR6, sk))
 		err = 0;
 	return err;
 }

net/ipv6/tcp_ipv6.c

@@ -508,7 +508,7 @@ static int tcp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 			tcp_ld_RTO_revert(sk, seq);
 	}
 
-	if (!sock_owned_by_user(sk) && np->recverr) {
+	if (!sock_owned_by_user(sk) && inet6_test_bit(RECVERR6, sk)) {
 		WRITE_ONCE(sk->sk_err, err);
 		sk_error_report(sk);
 	} else {

net/ipv6/udp.c

@@ -619,7 +619,7 @@ int __udp6_lib_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 		goto out;
 	}
 
-	if (!np->recverr) {
+	if (!inet6_test_bit(RECVERR6, sk)) {
 		if (!harderr || sk->sk_state != TCP_ESTABLISHED)
 			goto out;
 	} else {
@@ -1283,7 +1283,7 @@ static int udp_v6_send_skb(struct sk_buff *skb, struct flowi6 *fl6,
 send:
 	err = ip6_send_skb(skb);
 	if (err) {
-		if (err == -ENOBUFS && !inet6_sk(sk)->recverr) {
+		if (err == -ENOBUFS && !inet6_test_bit(RECVERR6, sk)) {
 			UDP6_INC_STATS(sock_net(sk),
 				       UDP_MIB_SNDBUFERRORS, is_udplite);
 			err = 0;
@@ -1608,7 +1608,7 @@ int udpv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 		up->pending = 0;
 
 	if (err > 0)
-		err = np->recverr ? net_xmit_errno(err) : 0;
+		err = inet6_test_bit(RECVERR6, sk) ? net_xmit_errno(err) : 0;
 	release_sock(sk);
 
 out:

net/sctp/ipv6.c

@@ -128,7 +128,6 @@ static void sctp_v6_err_handle(struct sctp_transport *t, struct sk_buff *skb,
 {
 	struct sctp_association *asoc = t->asoc;
 	struct sock *sk = asoc->base.sk;
-	struct ipv6_pinfo *np;
 	int err = 0;
 
 	switch (type) {
@@ -149,9 +148,8 @@ static void sctp_v6_err_handle(struct sctp_transport *t, struct sk_buff *skb,
 		break;
 	}
 
-	np = inet6_sk(sk);
 	icmpv6_err_convert(type, code, &err);
-	if (!sock_owned_by_user(sk) && np->recverr) {
+	if (!sock_owned_by_user(sk) && inet6_test_bit(RECVERR6, sk)) {
 		sk->sk_err = err;
 		sk_error_report(sk);
 	} else {